Proppants for hydrocarbon recovery

ABSTRACT

A method of sequestering at least one target species, including exposing a proppant for use in subterranean hydrocarbon recovery via hydraulic fracturing which comprises a material adapted to sequester the at least one target species formed external to the subterranean formation and formed external to the proppant and the material, at least one of (a) prior to injecting a fluid comprising the proppant into a subterranean fracture or (b) subsequent to injecting the fluid comprising the proppant into the subterranean fracture; or exposing the material of the proppant to the at least one target species prior to completing formation of the proppant.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is a divisional patent application of U.S. patentapplication Ser. No. 14/635,741, filed Mar. 2, 2015, which claimsbenefit of U.S. Provisional Patent Application Ser. No. 61/946,464,filed Feb. 28, 2014, the disclosures of which are incorporated herein byreference.

BACKGROUND

The following information is provided to assist the reader inunderstanding technologies disclosed below and the environment in whichsuch technologies may typically be used. The terms used herein are notintended to be limited to any particular narrow interpretation unlessclearly stated otherwise in this document. References set forth hereinmay facilitate understanding of the technologies or the backgroundthereof. The disclosure of all references cited herein are incorporatedby reference.

In general, a proppant is a solid material designed to maintain aninduced hydraulic fracture open, either during or after a fracturingprocess. Proppants are added to fracking fluids which are injected intosubterranean formations. Fracking fluids vary in composition dependingon the type of fracturing. Proppants may, for example, include treatedsand, man-made ceramic materials and/or polymers. Current trends infracking proppant selection have shifted from the use of silica sand tothe use of high strength ceramic particles for deep well completionsoperations. This trend is based primarily of the strength and sizeconformation of the proppant material.

SUMMARY

In one aspect, a method of hydraulic fracturing in a subterraneanformation (to open a fracture therein) includes injecting a fluidincluding a proppant into the subterranean formation, wherein theproppant includes a material adapted to sequester at least one targetspecies, and exposing or contacting at least one of the proppant or thematerial to/with the at least one target species either prior toinjecting the proppant or subsequent to injecting the proppant. The atleast one target species may, for example, be carbon dioxide, othergaseous species such as acid gases, or one or more components ormaterials present in flow-back water. As used herein, the term“sequester” refers to capturing or fixing a species via interactiontherewith (for example, via reaction, adsorption, capture, encapsulationetc.).

In a number of embodiment, the target species may for example beabsorbed upon exposure of at least one of the proppant or the materialto a fluid (including, a liquid or a gas). In a number of embodiments,at least one of the proppant or the material is exposed to, for example,emissions from a combustion system for a hydrocarbon to expose theproppant or the material to the at least one target species. In a numberof embodiments, the fluid including the proppant is injected and the atleast one target species is pumped into the fracture after injection ofthe fluid including the proppant to sequester the at least one targetspecies within the fracture. The proppant or the material may, forexample, be exposed to the at least one target species prior toinjecting the fluid including the proppant and the fluid including theproppant is thereafter injected to sequester the at least one targetspecies within the fracture.

The material may, for example, be at least 55% by weight of theproppant, at least 75% by weight of the proppant, at least 85% by weightof the proppant, or at least 95% by weight of the proppant. In a numberof embodiments, the material may be approximately 100% by weight of theproppant. The material may, for example, be selected from the groupconsisting of sodium bicarbonates, calcium bicarbonates, olivine,dunite, pyroxene, magnesium silicate, ankerite, dawsonite, serpentine,calcium oxides, magnesium oxides, magnesite, siderite, and dolomite.

In a number of embodiments, the at least one of the proppant includes abulk proppant core and a layer outside the core which includes thematerial adapted to sequester the at least one target species. The atleast one proppant may further include a completions layer outside thelayer including the material adapted to sequester the at least onetarget species. The completions layer may, for example, (at leasttemporarily) provide the functionalized proppant wither propertiesdesirable for the completions routine and/or may protect the layerincluding the material adapted to sequester the at least on targetspecies during completions processes.

In another aspect, a method of sequestering at least one target speciesincludes:

-   -   (i) exposing a proppant for use in subterranean hydrocarbon        recovery via hydraulic fracturing which includes a material        adapted to sequester the at least one target species at least        one of (a) prior to injecting a fluid including the proppant        into a subterranean fracture or (b) subsequent to injecting the        fluid including the proppant into the subterranean fracture; or    -   (ii) exposing the material of the proppant to the at least one        target species prior to completing formation of the proppant.

In a further aspect, a proppant is formed by incorporating a material inthe proppant adapted to absorb/sequester at least one target species andexposing at least one of the material or the proppant including thematerial to the target species.

In still a further aspect, a proppant for use in hydraulic fracturing ina subterranean formation to prop a fracture therein includes a materialadapted to sequester at least one target species.

The present devices, systems, methods and compositions, along with theattributes and attendant advantages thereof, will best be appreciatedand understood in view of the following description taken in conjunctionwith any accompanying drawings.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 illustrates a bar graph showing greenhouse gas emissions over thelife cycle of natural gas production and combustion.

FIG. 2 illustrates schematically a hydraulically fractured well for theproduction of, for example, natural gas and the pumping of combustionemissions from an electric power plant into the well for thesequestration of, for example, carbon dioxide in a functionalizedproppant.

FIG. 3A illustrates the use of a functionalized proppant to prop ahydraulically fractured fissure and the sequestration of carbon dioxidein the functionalized proppant.

FIG. 3B illustrates chemical reactions via which carbon dioxide may besequestered using the mineral olivine or the mineral serpentine.

FIG. 4 illustrates an embodiment of an engineered or composite proppantincluding a layer of functionalized material.

DESCRIPTION

It will be readily understood that the components of the embodiments, asgenerally described herein and/or illustrated in the figures herein, maybe arranged and designed in a wide variety of different configurationsin addition to the described representative embodiments. Thus, thefollowing description of representative embodiments or examples, is notintended to limit the scope of the embodiments, as claimed, but ismerely representative of embodiments hereof.

Reference throughout this specification to “one embodiment” or “anembodiment” (or the like) means that a particular feature, structure, orcharacteristic described in connection with the embodiment is includedin at least one embodiment. Thus, the appearance of the phrases “in oneembodiment” or “in an embodiment” or the like in various placesthroughout this specification are not necessarily all referring to thesame embodiment.

Furthermore, described features, structures, or characteristics may becombined in any suitable manner in one or more embodiments. In thefollowing description, numerous specific details are provided to give athorough understanding of embodiments. One skilled in the relevant artwill recognize, however, that the various embodiments can be practicedwithout one or more of the specific details, or with other methods,components, materials, et cetera. In other instances, well knownstructures, materials, or operations are not shown or described indetail to avoid obfuscation.

As used herein and in the appended claims, the singular forms “a,” “an”,and “the” include plural references unless the context clearly dictatesotherwise. Thus, for example, reference to “a material” includes aplurality of such materials and equivalents thereof known to thoseskilled in the art, and so forth, and reference to “the material” is areference to one or more such materials and equivalents thereof known tothose skilled in the art, and so forth. Recitation of ranges of valuesherein are merely intended to serve as a shorthand method of referringindividually to each separate value falling within the range. Unlessotherwise indicated herein, each separate value, as well as intermediateranges of values, are incorporated into the specification as ifindividually recited herein. All methods described herein can beperformed in any suitable order unless otherwise indicated herein orotherwise clearly contraindicated by the text.

In a number of embodiments hereof, proppant particles/materials areprovided for use, for example, in hydraulic fracturing (“fracking”)processes used for hydrocarbon recovery (for example, petroleum andnatural gas recovery in shale formations). In that regard, a number of“functionalized” proppants hereof exhibit appropriate physiochemicalproperties for use in fracking procedures (for example, exhibit suitablestrength and size for deep well completions) with one or more additionalproperties which can be utilized prior to fracking and/or inpost-completions processes/routines. For example, one or more materialsof the proppants hereof may absorb certain chemical/target species suchas carbon dioxide (CO₂), hydrogen sulfide (H₂S), carbon monoxide (CO)and/or other chemical species so that chemical such species can besequestered in subterranean formations under use of the proppant infracking processes. In a number of embodiments hereof, therepresentative example of absorbing and sequestering carbon dioxide isset forth.

In several such representative embodiments, a carbon dioxide absorbingor sequestering material is used in proppants hereof so that theproppant can be used to effect carbon dioxide absorption/sequestration.Examples of carbon dioxide-absorbing materials suitable for use hereininclude, but are not limited to, sodium bicarbonates, calciumbicarbonates, olivine, dunite, pyroxene, magnesium silicate, ankerite,dawsonite, serpentine, calcium oxides, magnesium oxides, magnesite,siderite, dolomite, and/or other similar carbon-adsorbing materials andminerals. The carbon dioxide absorbing or sequestering material hereofmay, for example, make up (by weight) at least 55%, at least 65%, atleast 75%, at least 85%, at least 95% or 100% of the proppant. Theproppants hereof may, for example, be manufactured directly from thematerials/minerals through, for example, grinding to achieve appropriatesize and shape distributions, or the proppants may be manufactured fromthe materials/minerals and derivatives thereof into, for example, acomposite system (for example, a ceramic) with composite properties.Processing of the materials/minerals in forming proppants should not,however, substantially limit the ability of the materials toabsorb/sequester CO₂ (and/or other target species to beabsorbed/sequestered) in the formed proppant in embodiments in which theformed proppant is to absorb/sequester CO₂. A number of desirableproperties of proppants are set forth in the international standard ISO13503-2 (API RP 19C) (the disclosure of which is incorporated herein byreference). A number of such properties are set forth in Table 1 belowto provide guidance in selecting carbon-absorbing/sequestering materialsfor use in proppants hereof. Table 1 also sets forth data for aminimally processed dunite sample.

Smaller proppants may spread farther into fractures and provide superiorconductivity. However, crush resistance is important to prevent crushingof the proppants into very small particles or “fines” which may lead todecreased conductivity. In general, spherical proppants handle higherstresses and resist crushing better than non-spherical proppants.Proppants should be transportable into fractures and fissures, becompatible with fracturing and wellbore fluids, allow acceptable cleanupof fracturing fluids and resist flowback. Other desirable properties ofproppants include thermal stability, chemical stability, environmentalsafety and ready availability. In addition to predetermining desirableproperties for fracturing proppants, the performance of proppants mayalso be studied under realistic conditions to, for example, measureconductivity and other characteristics under conditions that may beunique to a particular reservoir. Proppant characteristics andengineering of proppants is, for example, discussed in Lyle, D.,“Proppants Open Production Pathways,” E&P, Hart Energy Publishing,Houston, Tex. (2011), the disclosure of which is incorporated herein byreference.

In a number of embodiments, a producing well in which the proppantshereof are used in a fracking fluid may feed methane and/or otherhydrocarbon(s) to one or more combustion systems. Subsequently,emissions (or a portion/fraction thereof) from the combustions systemmay be pumped into or “cycled back” to the well/fracture to effectpermanent sequestration of at least one target species in the emissionsvia interaction with the proppants hereof. The adsorption of the atleast one target species of the combustion emissions by the proppantshereof may, for example, result in proppant hardening and/or swelling,which can further enhance recovery from the producing formation.Alternatively, the materials/minerals of the proppants hereof or themanufactured proppants can be exposed to combustion emissions (or aportion/fraction thereof) prior to inclusion of the proppants in afracking fluid so that such at least one target species from theemissions is sequestered upon use of the proppants. One or morechemically interactive or reactive species may, for example, be appliedto or immobilized on proppants hereof to enhance hydrocarbon recovery,enhance emission sequestration, or to otherwise interact withrecovery/production fluids.

TABLE 1 ISO 13503-2 Property Standard Dunite Turbidity (NTU) ≦250 243Krumbein Shape Factors Roundness ≧0.6 0.5 Sphericity ≧0.6 0.5 Clusters(%) ≦1.0 0 Bulk Density (g/cc) 1.33 Bulk Density (lb/ft

) 83.22 Specific Gravity 2.62 Particle Size Distribution, mm Sieve 1.18016 ≦0.1 0.1 0.850 20 35.5 0.710 25 30.6 0.600 30 22.3 0.500 35 9.8 0.42540 1.0 0.300 50 0.1 <0.300 Pan ≦1.0 0.6 Total 100.0 % In Size ≧90 63.7Mean Particle Diameter, mm 0.773 Median Particle Diameter (MPD), mm0.751 Solubility in12/3 HCL/HF for 0.5 HR @ 150° F. ≦2.0 33.8 (% WeightLoss) Settling Rate (ft/min) 93.9 Crush Properties ISO Crush Analysis (%Fines) ≦10 15.8 4 lb/ft 2@ 2,000 psi

indicates data missing or illegible when filed

A number of benefits are provided by using the proppants hereof inmodern fracking procedures (for example, in hydraulically fracturedshale formations). The functionality of the proppant may, for example,be made to enhance production from the formation during or aftercompletions routines. Moreover, the functionalized proppants hereof mayalso, and in some cases concurrently, react with or otherwisefix/sequester unwanted byproducts associated with the production or useof recovered hydrocarbons (such as combustion emissions and contaminatedflow-back water) to permanently fix such byproducts within the producingformation. Such benefits may increase well production, enhanceprofitability and/or reduce waste impact of hydraulically fracturedreservoirs (for example, shale oil and/or gas reservoirs).

Materials in flow-back water which may be fixed/sequestered byfunctionalized proppants hereof include, but are not limited to, clays,chemical additives, dissolved metal ions, total suspended particles(TSP), total dissolved solids (TDS), and radioactive materials. TDS may,for example, include sodium, magnesium, potassium, and other salts aswell as minerals including but not limited to barium, calcium, and iron.TSP may, for example, include clay, minerals, and other colloidalparticles. Dissolved metal ions may, for example, include copper, iron,lead, cobalt, and chromium. Chemical additives may, for example, includegelling agents, scale inhibitors, breakers, crosslinkers, biocides,corrosion inhibitors, acids, friction reducers, surfactants, and salts.Radioactive materials (in the case of produced water) may, for example,include radium isotopes.

Functional materials for inclusion into proppants for interaction withmaterial in flow-back water may, for example, include proteins, enzymes,bentonite, activated carbon, chitin, acids, bases, synthetic polymer andnatural polymers. The properties required of such functional materialsmay vary with the intended purpose. Functional proppants for interactionwith flow-back water may, for example, form a filter-likesuper-structure of packed functionalized proppants, where the propertyis achieved by either proppant placement and/or proppant materialsencouraging or facilitating binding under packing conditions.

The use of the functionalized fracking proppant technology hereofrepresents a paradigm shift in the progression of engineered frackingproppants. Currently available advanced engineered proppants areoptimized for only primary production productivity, while thefunctionalized proppants hereof offer, for example, preproduction,secondary production and/or post completions functionality. In thatregard, the functionalized fracking proppants hereof not only improve ormaximize well productivity through controlled shape and hardness, butare also chemically designed for preproduction, secondary productionand/or post completions functionality.

FIG. 1 illustrates a study of greenhouse gas emissions over thelife-cycle of the production and combustion of natural gas from afracking operation. As seen from FIG. 1, the majority of greenhouse gasemissions arise from CO₂ emitted during the combustions cycle. Althoughnatural gas is one of the cleanest fuels for the efficient production ofelectricity, the life cycle greenhouse gas emissions associatedtherewith are higher than a number of alternative energy options such assolar power, wind power and nuclear power.

FIGS. 2 and 3A schematically illustrate the fracking process and the useof functionalized fracking proppants hereof to sequester, for example,CO₂ from an electric power plant within hydraulic fractured strata. Inhydraulic fracturing or fracking, a high-pressure fluid is injected intoa wellbore to create cracks, fractures or fissures in the deep-rockformations through which natural gas, petroleum, and brine will flowmore freely. After the hydraulic pressure is removed from the well,small grains of hydraulic fracturing proppants hold the fissures open(see, for example, FIG. 3A). As illustrated in FIG. 2, natural gasturbine exhaust from an electric power plant can be cycled back into acompleted hydraulic fracking reservoir. As illustrated in FIG. 3A, theproppant carbonized, altering physical properties thereof, which maypotentially benefit secondary production from the well. FIG. 3Billustrates chemical reactions of the representative examples of olivineand serpentine that demonstrate how the functionalized proppants hereofare carbonized. By sequestering CO₂ from the electric power plant viacarbonization of the functionalized proppants hereof, the electricityproduced from the electric power plant has lower effective carbonemissions.

As seen from Table 1, various materials such as dunite used infunctionalize fracking proppants hereof may not possess physicalcharacteristics that are optimized for use as fracking proppants. In anumber of embodiments, such minerals or materials may be incorporatedinto an engineered fracking proppant using engineering principlesdeveloped in the fracking proppant arts to improve or optimizeproperties desirable for fracking proppants such as sphericity andhardness/crushing resistance. FIG. 4 illustrates a representativeexample of an engineered proppant 10 hereof incorporating a functionalor functionalized material layer 20 (for example, functional tosequester a species such as CO₂, provide flow-back water treatmentand/or enhance secondary recovery), a bulk proppant material core 30 andan outer completions layer 40. Completions layer or surface 40 providesfunctionality for well completion and may provide chemical isolation offunctional material layer 20. Bulk proppant material core 30 may, forexample, provide bulk material properties desirable for completionsprocesses, including, for example, mechanical properties/strength andconformation/shape. Bulk proppant material core 30 may, for example, bea silica sand or a sintered or ceramic material as known in thefracturing proppant arts. Completions layer 40 may, for example, be apolymeric or resin layer as known in the fracturing proppant arts.

Completions layer 40 may, for example, include or be formed of apermeable, removable, or degrading material that, at least temporarilyprovides the functionalized proppant wither properties desirable for thecompletions routine. For example, completions layer 40 of functionalizedproppant 10 hereof may contain or form a coating that is not dissolvablein an acidic environment (for example, within HCl) which prevents thefunctionalized surface, or remaining subsurface (for example dunite,etc.) from dissolving in acidic completions fluids. Completions layer 40may, for example, later be removed via, for example, flushing a chemicaladditive subsequent to the completions routine, degrade naturally, or bedesigned to be permeable to the sequestered species (for example, CO₂).Once again, completions layer 40 may include resins and polymers. Anengineered proppant such as proppant 10 may, for example, bemanufactured using applied engineering principles via sintering,application of coatings, drying, and physical compaction.

The foregoing description and accompanying drawings set forth a numberof representative embodiments at the present time. Variousmodifications, additions and alternative designs will, of course, becomeapparent to those skilled in the art in light of the foregoing teachingswithout departing from the scope hereof, which is indicated by thefollowing claims rather than by the foregoing description. All changesand variations that fall within the meaning and range of equivalency ofthe claims are to be embraced within their scope.

What is claimed is:
 1. A method of sequestering at least one targetspecies, comprising: (i) exposing a proppant for use in subterraneanhydrocarbon recovery via hydraulic fracturing which comprises a materialadapted to sequester the at least one target species formed external toa subterranean formation and formed external to the proppant and thematerial, at least one of (a) prior to injecting a fluid comprising theproppant into a subterranean fracture or (b) subsequent to injecting thefluid comprising the proppant into the subterranean fracture; or (ii)exposing the material of the proppant to the at least one target speciesprior to completing formation of the proppant.
 2. The method of claim 1wherein the at least one target species is carbon dioxide.
 3. The methodof claim 1 wherein the at least one target species is a material presentin flow-back water.
 4. The method of claim 2 wherein at least one of theproppant or the material is exposed to emissions from a combustionsystem including the at least one target species.
 5. The method of claim1 wherein the fluid comprising the proppant is injected and the at leastone target species is pumped into the subterranean formation afterinjection of the fluid comprising the proppant to sequester the at leastone target species within the subterranean formation.
 6. The method ofclaim 1 wherein at least one of the proppant or the material is exposedto the at least one target species prior to injecting the fluidcomprising the proppant, and the fluid comprising the proppant isthereafter injected to sequester the at least one target species withinthe subterranean formation.
 7. The method of claim 1 wherein thematerial is selected from the group consisting of sodium bicarbonates,calcium bicarbonates, olivine, dunite, pyroxene, magnesium silicate,ankerite, dawsonite, serpentine, calcium oxides, magnesium oxides,magnesite, siderite, and dolomite.
 8. The method of claim 2 wherein thematerial is selected from the group consisting of sodium bicarbonates,calcium bicarbonates, olivine, dunite, pyroxene, magnesium silicate,ankerite, dawsonite, serpentine, calcium oxides, magnesium oxides,magnesite, siderite, and dolomite.
 9. The method of claim 1 wherein thematerial comprises at least 55% by weight of the proppant.
 10. Themethod of claim 1 wherein the proppant comprises a bulk proppant coreand a layer outside the bulk proppant core comprising the materialadapted to sequester the at least one target species.
 11. The method ofclaim 10 wherein the proppant further comprises a completions layeroutside the layer comprising the material adapted to sequester the atleast one target species, the completions layer providing protection tothe layer comprising the material adapted to sequester the at least ontarget species during completions processes.
 12. A proppant for use inhydraulic fracturing in a subterranean formation to prop a fracturetherein, comprising a material adapted to sequester at least one targetspecies formed external to the subterranean formation and formedexternal to the proppant and the material.
 13. The proppant of claim 12wherein the at least one target species is carbon dioxide.
 14. Theproppant of claim 12 wherein the material is selected from the groupconsisting of sodium bicarbonates, calcium bicarbonates, olivine,dunite, pyroxene, magnesium silicate, ankerite, dawsonite, serpentine,calcium oxides, magnesium oxides, magnesite, siderite, and dolomite. 15.The proppant of claim 13 wherein the material is selected from the groupconsisting of sodium bicarbonates, calcium bicarbonates, olivine,dunite, pyroxene, magnesium silicate, ankerite, dawsonite, serpentine,calcium oxides, magnesium oxides, magnesite, siderite, and dolomite. 16.The proppant of claim 15 wherein the material comprises at least 55% byweight of the proppant.
 17. The proppant of claim 14 further comprisinga bulk proppant core and a layer outside the bulk proppant corecomprising the material adapted to sequester the at least one targetspecies.
 18. The proppant of claim 17 further comprising a completionslayer outside the layer comprising the material adapted to sequester theat least one target species, the completions layer providing protectionto the layer comprising the material adapted to sequester the at leastone target species during completions processes.